This invention relates to the conversion of methane to higher hydrocarbons. A particular application of this invention is a method for converting natural gas to more readily transportable material.
Methane can be converted to higher hydrocarbons by reaction at conditions of elevated temperature--e.g. a temperature selected within the range from about 500.degree. C. to about 1000.degree. C. For example, methane can be contacted with an oxidative synthesizing agent containing a reducible metal oxide at such elevated temperatures in order to produce higher hydrocarbons. Reducible oxides of several metals have been identified which are capable of converting methane to higher hydrocarbons. In particular, oxides of manganese, tin, indium, germanium, lead, antimony, bismuth, praseodymium, terbium, cerium, iron and ruthernium are most useful. See commonly-assigned U.S. Pat. Nos. 4,443,644 (Sb); 4,443,649 (Mn); 4,444,984 (Sn); 4,445,648 (In); 4,443,645 (Ge); 4,443,674 (Pb); 4,443,646 (Bi); 4,499.323 (Pr); 4,499,324 (Ce); and 4,593,139 (Ru), the entire contents of which are incorporated herein by reference. See also commonly-assigned U.S. patent application Ser. No. 06/666,694 (Fe) now U.S. Pat. No. 4,721,828 the entire content of which is incorporated herein by reference.
Commonly-assigned U.S. Pat. No. 4,554,395 discloses and claims a process which comprises contacting methane with an oxidative synthesizing agent under elevated pressure (2-100 atmospheres) to produce greater amounts of C.sub.2 +hydrocarbon products.
Commonly-assigned U.S. Pat. No. 4,560,821 discloses and claims a process for the conversion of methane to higher hydrocarbons which comprises contacting methane with particles comprising an oxidative synthesizing agent which particles recirculate between two physically separate zones--a methane contact zone and an oxygen contact zone.
U.S. Pat. No. 4,499,322 discloses and claims a process for the conversion of methane to higher hydrocarbon and comprises contacting methane with an oxidative synthesizing agent containing a promoting amount of alkali metal and/or compounds thereof.
U.S. Pat. No. 4,495,374 discloses and claims a process for the conversion of methane to higher hydrocarbons which comprises contacting methane with an oxidative synthesizing agent containing a promoting amount of alkaline earth metal and/or compounds thereof.
Hinsen and Baerns report studies of a continuous mode for the oxidative coupling of methane wherein regeneration air is cofed with methane feed. Hinsen, W. and Baerns, M., "Oxidative Koppling von Methan zu C.sub.2 -- Kohlenwasserstoffen in Gegenwart unterschiedlicher Katalsatoren", Chemiker-Zeitung, Vol. 107, No. 718, pp. 223-226 (1983). Using a catalyst based on lead oxide and gamma-alumina in a fixed bed reactor operated at 1 atmosphere total pressure and 600-750 degrees C., they report results of approximately 53% selectivity to ethane and ethylene at 8% methane conversion for a feed consisting of about 50% methane, 25% air and 25% nitrogen. Other metal oxides studied by Hinsen and Baerns included oxides of Bi, Sb, Sn and Mn.
U.S. Pat. No. 4,523,049, discloses and claims a process for converting methane to higher hydrocarbons which comprises contacting methane and an oxygen-containing gas with a solid comprising a reducible metal oxide and an alkali/alkaline earth metal promotor.
U.S. Pat. No. 4,523,050 discloses and claims a process for converting methane to higher hydrocarbons which comprises contacting methane and an oxygen-containing gas with a manganese silicate.
Commonly-assigned copending U.S. patent application Ser. No. 07/014406 filed Feb. 13, 1987 discloses and claims a method for converting methane to higher hydrocarbons wherein methane and added water are contacted in the substantial absence of added gaseous oxidant with a solid comprising at least one reducible metal oxide.
Commonly-assigned copending U.S. patent application Ser. No. 07/014405 filed Feb. 13, 1987 discloses and claims a method for converting methane to higher hydrocarbons wherein methane and a gaseous oxidant together with added water are contacted with a non acidic solid and/or a reducible metal oxide.
The reaction products of the foregoing processes are hydrocarbons, carbon oxides, coke and water.
The methane conversion reaction can be carried out by contacting methane with the reducible metal oxide in the fluidized bed reaction systems as well as in fixed bed systems.
A problem in the past has been that the catalysts employed have not had entirely satisfactory characteristics of fluidity, strength, density, attrition resistance and heat conductivity while also possessing appropriate oxygen transfer activity.